1. Field of the Invention
This invention provides a new negative resist for use in the preparation of microelectronics using electron beams and other forms of irradiation.
2. Description of the Prior Art
The use of radiation sensitive polymers as resists in the fabrication of certain microelectronic devices and circuits has been known for some time. An excellent review of certain requirements of the state of this art is contained in an article by Murrae J. Bowden entitled "Electron Irradiation of Polymers and Its Application to Resist for Electron-Beam Lithography" published in CRC Critical Reviews Solid State Sciences at pp. 223 et. seq. in February of 1979.
Materials known to function as resist in the prior art include, but are not limited to, polymers bearing epoxide groups, such as poly(glycidyl methacrylate), glycidyl methacrylate copolymers, and epoxidized polybutadiene; polymers bearing olefinic groups, such as poly(diallyl phthalate), allyl esters of vinyl ethermaleic anhydride copolymers, polybutadiene, and various olefinic photoresists; and less sensitive materials such as polymethylsiloxane, polystyrenes, poly(vinyl chloride), poly(vinyl acetate), poly (methyl vinyl ketone), and poly(vinylferrocene).
Negative resists were disclosed by Saburo Imamura in an article entitled "Chloromethylated Polystyrene as a Dry Etching Resistant Negative Resist for Sub Micron Technology" that was published in the Journal of the Electrochemical Society: SOLID STATE SCIENCE AND TECHNOLOGY, 1979.
Other relevant prior art, to the invention described below, is disclosed in an article entitled "Experimental Observations of Nearly Monodisperse Polystyrene as Negative Electron Resist" by Joey H. Lai et al, Journal of the Electrochemical Society: SOLID STATE SCIENCE AND TECHNOLOGY, Vol. 126, No. 4, page 696 in April of 1979. Still other equally relevant prior art is embodied in an article entitled "Polymeric Electron Beam Resist" by H. Y. Ku et al published in Journal of the Electrochemical, Society: SOLID STATE SCIENCE in July of 1969, at page 980 et. seq. And, the article entitled "Contrast in the Electron Beam Lithography of Substituted Aromatic Homopolymers and Copolymers" by E. D. Feit et al was published Nov/Dec 1979 in the Journal Vacuum Science Technology similarly describes polystyrene resists which are structurally very similar to the resist of the present invention.
However, it is apparent from the above-mentioned articles that a negative working resist prepared with polystyrene is relatively insensitive and is therefore often unsuitable for practical applications in the design and fabrication of certain types of microelectronic circuits.
While the above-mentioned prior resists have met with a measure of success, there is still a need for negative working electron beam resists having higher sensitivities than those of the above prior art and which are susceptible of being developed into fine line images after exposure to incident forming radiation. It is the fulfillment of this need to which the present invention is directed.